Comparison of Methods for Calculating Turbine Work in the Air Turborocket


The air turborocket (ATR) is an airbreathing propulsion system that utilizes a turbine-drive gas source, which also provides fuel for the main combustor. By making some simplifying assumptions, ATR specific impulse becomes largely a function of turbine specific work and main-combustor gas total temperature, Turbine specific work is the major driver of ATR specific impulsebecause it also determines the main-combustor fuel-to-air ratio. Turbine specific work can he calculated assuming the turbine-drive gas is an equilibrium gas mixture, which expands without reaction, a nonreacting gas mixture, or an equilibrium gas mixture, which expands with reaction. Turbine work,main-combustor gas total temperature, and specific impulse based on these assumptions are compared, Significant errors in specific impulse result if an equilibrium, nonreacting gas mixture is assumed. This assumption can also lead to the mistaken conclusion that there are two maximum specific-impulse values at significantly different gas-generator oxidizer-to-fuel ratios. By assuming a reacting gas mixture, it is shown that the maximum specific-impulse of an O-2/H-2 driven ATR occurs at a gas-generator oxidizer-to-fuelratio of about 4. There are two possible maximum specific-impulse values for the O-2/propane-driven ATR at gas-generator oxidizer-to-fuel ratios of about 1 and 2.


Mechanical and Aerospace Engineering

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Article - Journal

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© 2001 American Institute of Aeronautics and Astronautics (AIAA), All rights reserved.

Publication Date

01 Jan 2001